Magnetic arc vent seal

ABSTRACT

Method and apparatus for sealing an air vent in a switchgear cabinet provide a vent seal assembly having a vent seal cover and a set of linear guides on which the vent seal cover may be mounted. The vent seal cover and linear guides are housed within a casing attachable to an interior surface of the switchgear cabinet and directly over an air vent. Within the casing, the vent seal cover may slide freely along the linear guides toward the air vent, with no spring or other mechanical biasing mechanism to oppose the sliding of the cover. A catch on the casing releasably holds the vent seal cover to keep the air vent open during normal operating conditions. When an arc event occurs, pressure from the arc event knocks the vent seal cover free of the catch and propels it toward the air vent, quickly slamming the air vent shut.

FIELD OF THE INVENTION

The disclosed embodiments relate generally to switchgear and similarelectrical isolation equipment, and particularly to methods andapparatuses for quickly sealing the cabinets of such isolationequipment.

BACKGROUND OF THE INVENTION

Switchgear and similar electrical isolation equipment are highlyregulated by industry standards (e.g., IEEE, ANSI, etc.). Among otherthings, these standards specify how much temperature may rise within aswitchgear cabinet and the maximum allowable temperature. To comply withthe temperature limitations, ventilation is used in certain switchgearto improve ambient air flow through the switchgear cabinet. For example,in smaller switchgear like the HVL/cb™ series of metal-enclosedswitchgear from Schneider Electric USA, Inc., air vents may be providedon the front door of the cabinet near the bottom thereof and on the backcover of the cabinet near the top thereof to create cross flowventilation through the cabinet.

The air vents, however, can cause the switchgear not to pass certainindustry safety standards. For example, in order for switchgear to beconsidered arc resistant under industry standards, the switchgearcabinet must not allow arc blast to escape during an arc event, as thehot arc blast can cause significant damage to nearby equipment andpersonnel. Some air vents therefore include a vent cover that remainsopen under normal operating conditions, but immediately closes uponoccurrence of an arc event to seal the switchgear cabinet and therebycontain the arc event within the cabinet.

To keep the vent cover open, existing air vents employ a spring orsimilar mechanical biasing mechanism that continuously pushes orotherwise maintains the vent cover in an open position. When an arcevent occurs, the resulting pressure surge forces the vent cover into aclosed position, compressing the spring or other mechanical biasingmechanism in the process. As the spring or biasing mechanism compresses,it pushes with progressively greater force against the vent cover in adirection opposite the compression. The increase in resistance from thespring or biasing mechanism can cause the vent cover not to closeimmediately and/or completely during an arc event, potentially allowingarc blast to escape from the cabinet and creating a safety hazard fornearby equipment and personnel.

Thus, a need exists for a more effective way to close air vents in thecabinets of switchgear and similar electrical isolation equipment.

SUMMARY OF THE DISCLOSED EMBODIMENTS

The embodiments disclosed herein are directed to a method and apparatusfor sealing air vents in switchgear and similar electrical isolationequipment. The method and apparatus provide a vent seal assembly havinga vent seal cover and a set of linear guides on which the vent sealcover may hang or otherwise be mounted. The vent seal cover and thelinear guides are housed within framing, which may be a generallyrectangular open-sided casing, that is attachable to an interior surfaceof a switchgear cabinet directly over an air vent in the cabinet. Withinthe casing, the vent seal cover may slide freely along the linear guidestoward and away from the air vent, with no spring or other mechanicalbiasing mechanism to resist the sliding of the cover in eitherdirection. A catch mechanism on the casing releasably holds the ventseal cover against the casing away from the air vent to keep the airvent open during normal operating conditions. When an arc event occurs,blast pressure from the arc event knocks the vent seal cover free of thecatch mechanism and propels it toward the air vent, quickly slamming thevent seal cover shut against the air vent and cutting off further airflow through the air vent.

In some embodiments, the generally rectangular casing may be constructedof two generally flat opposing frame members, a front or vent-side framemember and a rear or cabinet-side frame member. The two frame membersare similar or the same in size, with each frame member resembling atypical picture frame or window frame insofar as each frame memberdefines a generally rectangular window or opening that is similar or thesame as the window or opening in the opposing frame member. Supportbraces extending perpendicularly from one of the frame members, forexample, the rear frame member near the corners thereof keep the twoframe members separated from one another by a predefined distance toform the casing.

Within the casing, the linear guides, which may be simple roll pins insome embodiments, extend between the two frame members substantiallyperpendicularly thereto near the corners thereof. The roll pins suspendor otherwise support the vent seal cover, which may be a generallyrectangular sheet of fiberglass, within the casing substantiallyparallel to the frame members and hence substantially parallel to theair vent. This arrangement allows the vent seal cover to slide freelyback and forth along the linear guides toward and away from the airvent, meaning it does not require a greater or lesser amount of force tomove the vent seal cover in one direction compared to the other undernormal operating conditions.

In some embodiments, the catch mechanism that releasably holds the ventseal cover to keep the air vent open during normal operation may bemounted on the rear frame member of the casing. Any suitable catchmechanism capable of a quick release may be used to keep the air ventopen, such as a magnet-based catch analogous to the type widely used tokeep doors closed in room furniture, kitchen cupboards, and the like.Although a single magnet-based catch may suffice, preferably two suchmagnet-based catches are attached to the rear frame member of thecasing, one on the upper portion and one on the lower portion of theframe member. Ferrous metal plates may then be attached to the vent sealcover at locations corresponding to the locations of the magnet-basedcatches for magnetically engaging the catches. Alternatively, themagnet-based catches may be mounted on the vent seal cover and the metalplates may be mounted on the rear frame member.

In general operation, the front frame member of the casing is mounted onan interior surface of the switchgear cabinet directly over an air vent,for example, the air vent on the lower portion of the front door and/orthe upper portion of the back cover of the cabinet. During normaloperating conditions, the vent seal cover is held against the rear framemember by the magnet-based catches, allowing air to flow through thewindow or opening in the front frame member and hence through the airvent. When an arc event occurs in the switchgear cabinet, the pressurefrom the arc event explodes through the window or opening in the rearframe member, knocking the vent seal cover free of the magnet-basedcatches and propelling it toward the front frame member. As there is nofurther resistance at this point other than surface friction from theroll pins, the vent seal cover immediately slams into the front framemember, quickly cutting off further air flow through the front framemember and hence through the air vent.

In some embodiments, a generally rectangular gasket or similar liner maybe disposed around the window or opening of the front frame member onthe side facing the vent seal cover to provide an airtight seal betweenthe front frame member and the vent seal cover.

In general, in one aspect, the disclosed embodiments relate to a ventseal assembly. The vent seal assembly comprises, among other things, agenerally rectangular casing composed of a generally flat front framemember spaced apart by a predefined distance from a generally flat rearframe member, each frame member defining a generally rectangular windowtherein. The vent seal assembly also comprises linear guides extendingbetween the front frame member and the rear frame member substantiallyperpendicular thereto, each linear guide positioned near a corner of thefront frame member and the rear frame member. The vent seal assemblyfurther comprises a generally rectangular vent seal cover slidablymounted on the linear guides between the front frame member and the rearframe member substantially parallel thereto. A catch mechanism may bemounted on the rear frame member and configured to releasably hold thevent seal cover against the rear frame member to allow air flow throughthe window in the front frame member.

In general, in another aspect, the disclosed embodiments relate to anarc resistant switchgear cabinet. The arc resistant switchgear cabinetcomprises, among other things, an air vent located at an exteriorsurface of the switchgear cabinet, and a vent seal assembly mounted onan interior surface of the switchgear cabinet directly over the airvent. The vent seal assembly includes a vent seal cover slidablydisposed therein, the vent seal cover being held away from the air ventunder normal operating conditions and sliding freely toward the air ventto block air flow through the air vent upon occurrence of an arc event.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the disclosed embodiments willbecome apparent upon reading the following detailed description and uponreference to the drawings, wherein:

FIG. 1 is a front view of several switchgear cabinets having a vent sealassembly therein according to some implementations of the disclosedembodiments;

FIGS. 2A, 2B, and 2C are front, side, and rear views, respectively, of acabinet door on which a vent seal assembly may be mounted according tosome implementations of the disclosed embodiments;

FIG. 3 is a perspective view of an exemplary vent seal assemblyaccording to some implementations of the disclosed embodiments;

FIG. 4 is a perspective view of a rear frame member of a vent sealassembly according to some implementations of the disclosed embodiments;

FIG. 5 is a perspective view of a vent seal cover of a vent sealassembly according to some implementations of the disclosed embodiments;and

FIG. 6 is a perspective view of a front frame member of a vent sealassembly according to some implementations of the disclosed embodiments.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

As an initial matter, it will be appreciated that the development of anactual, real commercial application incorporating aspects of thedisclosed embodiments will require many implementation specificdecisions to achieve the developer's ultimate goal for the commercialembodiment. Such implementation specific decisions may include, andlikely are not limited to, compliance with system related, businessrelated, government related and other constraints, which may vary byspecific implementation, location and from time to time. While adeveloper's efforts might be complex and time consuming in an absolutesense, such efforts would nevertheless be a routine undertaking forthose of skill in this art having the benefit of this disclosure.

It should also be understood that the embodiments disclosed and taughtherein are susceptible to numerous and various modifications andalternative forms. Thus, the use of a singular term, such as, but notlimited to, “a” and the like, is not intended as limiting of the numberof items. Similarly, any relational terms, such as, but not limited to,“top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,”“side,” and the like, used in the written description are for clarity inspecific reference to the drawings and are not intended to limit thescope of the invention.

Referring now to FIG. 1, an exemplary switchgear system 100 is shownaccording to the disclosed embodiments composed of several modularswitchgear cabinets 102 a, 102 b, and 102 c. The particular switchgearsystem 100 shown here is a medium voltage switchgear, that is, a systemwith voltage ratings generally between 1 kV-35 kV. An example of such amedium voltage switchgear is the HVL/cb™ series of metal-clad switchgearfrom Schneider Electric USA, Inc., referenced above. It should of coursebe understood that the principles and concepts discussed herein are alsoapplicable to switchgear having lower and higher voltage ratings.

Each switchgear cabinet 102 a-c has a top front door 104, a bottom frontdoor 106, and a control panel (not expressly labeled) between the topand bottom front doors 104 and 106. An air vent 108 may be disposed onor in a lower portion of the bottom front door 106 in one or more of thecabinets 102 a-c for ventilation purposes in any necessary manner. Aswell, in some embodiments, an air vent 108 may also be disposed, forexample, on a back cover (not expressly shown) of one or more of thecabinets 102 a-c on the upper portion thereof to create cross flowventilation through the cabinet 102 a-c. As explained with respect toFIGS. 2A-2C, In accordance with the illustrated embodiment, a vent sealassembly 200 may be installed directly behind each air vent 108 toimmediately close off air flow through the air vent 108 upon occurrenceof an arc event. The vent seal assembly 200 may be mounted on aninterior surface of the switchgear cabinet 102 a-c, for example, on thebottom front door 106, or on some other interior surface of the cabinets102 a-c. In any case, the ability of the vent seal assembly 200immediately to close off air flow through the air vent 108 uponoccurrence of an arc event helps the switchgear cabinet 102 a-c to beconsidered as arc resistant.

Turning to FIGS. 2A-2C, the exemplary vent seal assembly 200 is shownmounted to the inside surface 202 of the bottom front door 106 of one ofthe switchgear cabinets 102 a-c. The vent seal assembly 200 ispositioned directly opposite the air vent 108, which is mounted on theoutside surface 204 of the bottom front door 106, as best seen in FIG.2B. A similar arrangement may be deployed for air vents 108 mountedelsewhere on the cabinet 102 a-c. But wherever it is mounted, the ventseal assembly 200 is flush against the surface of the cabinet 102 a-c soany air flow passing in or out of the air vent 108 must also passthrough the vent seal assembly 200.

FIG. 3 illustrates an exemplary implementation of the vent seal assembly200 according to the disclosed embodiments. In this example, the ventseal assembly 200 includes a generally rectangular open-sided (i.e.,having at least one side opening) casing 300 constructed of twogenerally flat opposing frame members: a front or vent-side frame member302 and a rear or cabinet-side frame member 304. It will be appreciatedthat the casing 300 might be other than a rectangular shape, such asother polygonal shapes or circular. The two frame members 302 and 304may be roughly the same size, with each frame member resembling atypical picture frame or window frame. Specifically, each frame member302 or 304 defines a generally rectangular window or opening 302 a and304 a (see FIGS. 4 and 6), respectively, that is similar or the same asthe window or opening in the opposing frame member 302 or 304. Supportbraces 306 extending perpendicularly from one of the frame members, forexample, the rear frame member 304 near the corners thereof, keep thetwo frame members 302 and 304 separated from one another by a predefineddistance “A,” which may be approximately 2.06 inches in someembodiments, such as for the above-mentioned HVL/cb™ metal-enclosedswitchgear or similar metal-enclosed and metal-clad switchgear, to formthe casing 300. The casing 300 may also have side slots 308 a and 308 bprovided on the sides of the casing 300 and a top slot 310 along the topof the casing 300 in some embodiments that facilitate air flow throughthe casing 300 under normal operating conditions.

A generally rectangular vent seal cover 312 is disposed within thecasing 300 between the front and rear frame members 302 and 304substantially parallel to the frame members (and hence substantiallyparallel to the air vent 108). The vent seal cover 312, which may be athin sheet of fiberglass material (e.g., GPO-3 fiberglass), may hang orbe otherwise suspended on linear guides 314 extending between the twoframe members 302 and 304, perpendicular thereto and at or near thecorners thereof. The linear guides 314 may be simple roll pins 314 inthe example shown here, but any suitable linear guide that allows thevent seal cover 312 to slide freely within the casing 300 toward or awayfrom the frame members 302 and 304 may be used without departing fromthe scope of the disclosed embodiments. Mounting plates 318 may bedisposed on one of the frame members, for example, the rear frame member304 near each corner thereof to secure the roll pins 314 within thecasing 300. The mounting plates 318 may receive one or more screws 320therein to fasten the plates 318 to the rear frame member 304 andthereby secure the roll pins 314.

A catch mechanism 322 may be mounted on the rear frame member 304 insome embodiments to keep the air vent 108 open during normal operatingconditions. Specifically, the catch mechanism 322 releasably holds thevent seal cover 312 against the rear frame member 304 (and hence awayfrom the air vent 108) to keep the air vent 108 open. In someembodiments, the catch mechanism 322 may be a magnet-based catch 324 ofthe type normally used to keep doors closed in room furniture, kitchencupboards, and the like. A single magnet-based catch 324 may be adequatein most embodiments, but preferably two such magnet-based catches 324are attached to the rear frame member 304, one on the upper portion nearthe middle thereof and one on the lower portion near the middle thereof.Ferrous metal plates 326 may then be attached to the vent seal cover 312at locations corresponding to the locations of the magnet-based catches324 for magnetically engaging the catches.

The use of magnet-based catches 324 in the foregoing embodiments avoidsthe need for springs or other mechanical biasing mechanisms in the ventseal assembly 200 that could oppose the sliding of the vent seal cover312 along the linear guides 314 or be less reliable to release. Thismeans the vent seal cover 312 can slide just as easily in one directionas in the other direction under normal operating conditions.Additionally, having two magnet-based catches 324 and mounting them inthe middle of the upper portion and lower portion of the rear framemember 304 allows the vent seal cover 312 to swivel slightly around anaxis “B” extending through the magnet-based catches 324. The swivelcreates a torque about the axis “B” that helps the vent seal cover 312more easily to break free of the magnet-based catches 324 than itotherwise could. It is also possible to achieve a similar result withthe magnet-based catches 324 mounted instead on the sides of the rearframe member 304 near the middles thereof. Alternatively, themagnet-based catches 324 may be mounted on vent seal cover 312 and themetal plates 326 mounted on the rear frame member 304 in someembodiments. Other catch mechanisms 322 of comparable speed andreliability to the magnet-based catches 324 may also be used to keep theair vent 108 open without departing from the scope of the disclosedembodiments.

In general operation, the casing 300 of the vent seal assembly 200 ismounted on an interior surface of a switchgear cabinet 102 a-c directlyover an air vent 108, for example, the air vent on the bottom front door106 (see FIGS. 2A-2C) and/or the back cover of the cabinet 102 a-c. Thecasing 300 may be so mounted via screws 330 on the front frame member302 near the corners thereof that fasten the front frame member 302 tothe switchgear cabinet 102 a-c. Once the vent seal assembly 200 ismounted, the vent seal cover 312 is slid back to the rear frame member304 where the magnet-based catches 324 hold the cover in place, allowingair to flow through the front frame member 302 and hence through the airvent. When an arc event occurs in the switchgear cabinet 102 a-c, theblast from the arc event knocks the vent seal cover 312 free of themagnet-based catches 324 and propels it toward the front frame member302. As there is no force opposing the vent seal cover 312 at this timebesides the surface friction from the roll pins 314, the vent seal cover312 immediately slams into the front frame member 302, quickly cuttingoff further air flow through the front frame member 302 and hencethrough the air vent 108. In some embodiments, a generally rectangulargasket or similar liner 328 may be disposed on the front frame member302 on the side facing the vent seal cover 312 to provide an airtightseal between the front frame member 302 and the vent seal cover 312.

An exemplary implementation of the rear frame member 304 is depicted inFIG. 4 according to some embodiments. As can be seen, the rear framemember 304 defines a window or opening 304 a through which arc blast mayenter to compel the vent seal cover 312 closed. The window or opening304 a may have a height “C” of approximately 8.12 inches in someembodiments, leaving a roughly one and a quarter inch border 332 aroundthe window 304 a. The overall height “D” of the rear frame member 304may be about 10.62 inches and the overall width “E” of the rear framemember 304 may be about 20.20 inches in some embodiments. Cutouts 334may be formed in the border 332 on the upper portion near the middlethereof and on the lower portion near the middle thereof for mountingthe catch mechanisms 322.

In the example shown here, the support braces 306 near the corners ofthe rear frame member 304 are part of a pair of opposing side supportwalls 336 a and 336 b extending perpendicularly from the sides of therear frame member 304. Like the rear frame member 304, the side supportwalls 336 a and 336 b resemble a picture frame or window frame insofaras each side support wall 336 a and 336 b define a side slot 308 a and308 b, respectively, therein. And while no top support wall is presentin the present embodiments, a bottom support wall 338 may be provided insome embodiments extending perpendicularly from the bottom of the rearframe member 304 to provide additional support for the casing 300. Sucha bottom support wall 338 may or may not have a bottom slot (notexpressly shown) formed therein.

FIG. 5 illustrates an example of the vent seal cover 312 according tosome embodiments. As mentioned earlier, the vent seal cover 312 may be agenerally rectangular sheet of thin fiberglass material, such as GPO-3fiberglass material. Where magnet-based catches 324 are used, metallicplates 326 may be attached or otherwise fastened to the vent seal cover312 on the upper portion near the middle thereof and on the lowerportion near the middle thereof to engage the magnet-based catches 324.Likewise, where roll pins 314 are used, holes 338 may be formed near thecorners of the vent seal cover 312 for mounting the vent seal cover 312on the roll pins 314. The holes 338 should be sufficiently large toallow the vent seal cover 312 to slide smoothly along the roll pins 314with few or no hitches. To this end, in some embodiments, the roll pins314 may be lubricated and/or the holes 338 may have ball bearingsdisposed therein to facilitate smooth sliding of the vent seal cover312.

FIG. 6 illustrates an exemplary implementation of the front frame member302 according to some embodiments. In this example, the front framemember 302 defines a window or opening 302 a therein that is about thesame size as the window or opening 304 a in the rear frame member 304,leaving a border 340 around the window 302 a that is about the same sizeas the border 332 (see FIG. 4) in the rear frame member 304. As well,the overall height and width of the front frame member 302 may be aboutthe same as the overall height and width of the rear frame member 304 insome embodiments. The generally rectangular gasket or liner 328mentioned earlier for facilitating an airtight seal may be disposed onthe front frame member 302 along the border 340 around the window oropening 302 a. Holes 342 may be provided near the corners of the frontframe member 302 to allow the front frame member 302 to be screwed orotherwise fastened to the switchgear cabinet 102 a-c via the screws 330(see FIG. 3).

While particular aspects, implementations, and applications of thepresent disclosure have been illustrated and described, variousalternatives exist that fall within the scope of the disclosedembodiments. Accordingly, it is to be understood that the presentdisclosure is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationsmay be apparent from the foregoing descriptions without departing fromthe embodiments as defined in the appended claims.

What is claimed is:
 1. An arc resistant switchgear cabinet, comprising: an air vent located at an exterior surface of the switchgear cabinet; and a vent seal assembly mounted on an interior surface of the switchgear cabinet directly over the air vent, the vent seal assembly including a vent seal cover slidably disposed therein, the vent seal cover being held away from the air vent under normal operating conditions; wherein the vent seal cover has side edges and all the side edges on the vent seal cover are held away from the air vent under the normal operating conditions, and wherein the vent seal cover, including all the side edges thereon, slides freely toward the air vent to block air flow through the air vent upon occurrence of an arc event.
 2. The switchgear cabinet of claim 1, wherein the air vent is located in a door of the switchgear cabinet.
 3. The switchgear cabinet of claim 1, wherein the vent seal assembly further includes a catch mechanism configured to releasably hold the vent seal cover away from the air vent to allow air flow through the air vent.
 4. The switchgear cabinet of claim 3, wherein the catch mechanism is a magnet-based catch.
 5. The switchgear cabinet of claim 4, further comprising a metallic plate mounted on the vent seal cover to engage the magnet-based catch.
 6. The switchgear cabinet of claim 5, wherein the linear guides are pins and the vent seal cover is suspended from the pins.
 7. The switchgear cabinet of claim 6, wherein the vent seal cover has a rectangular shape and is suspended from the pins via openings formed at each corner of the rectangular shape.
 8. The switchgear cabinet of claim 7, wherein the vent seal cover slides freely on the pins toward the air vent to block air flow through the air vent upon occurrence of an arc event.
 9. The switchgear cabinet of claim 1, wherein the vent seal assembly further includes linear guides and the vent seal cover is slidably mounted on the linear guides. 